Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014)
    Energy Harvesting & Storage Thursday Sessions
       Session EH-ThM

Paper EH-ThM4
Infrared Spectroscopic Study of Adsorption of Carbon Monoxide and Other Surface Reactions at the Ruthenium Dioxide Particle Film Aqueous Solution Interface

Thursday, December 11, 2014, 9:00 am, Room Lehua

Session: Nanotechnology & Energy
Presenter: Jim McQuillan, University of Otago, New Zealand
Authors: A.J. McQuillan, University of Otago, New Zealand
S. Aloi, University of Otago, New Zealand
Correspondent: Click to Email
Ruthenium dioxide is renown as a highly active oxidation catalyst as well as a material with supercapacitor properties. Its heterogeneous catalyst behaviour has been extensively studied in surface science using well-defined crystal faces under high vacuum conditions. These studies have led to a good understanding of its active sites and the roles they play in solid/gas interface reactions such as the oxidation of adsorbed carbon monoxide. At the same time, the importance of ruthenium dioxide as an electrocatalyst has led to many electrochemical studies of RuO2 electrodes immersed in aqueous solutions. These studies, somewhat contrasting with those in surface science, have sought to elucidate the basis of the ‘pseudocapacitor’ behaviour of hydrous RuO2 which must involve both faradaic and non-faradaic processes. In spite of extensive efforts the details of the electron and proton transfer processes at RuO2 electrodes remain obscure and there have been few spectroscopic studies addressing questions about the molecular nature of processes at the hydrous RuO2 interface.

We have used in situ attenutated total reflection infrared (ATR-IR) spectroscopy to examine hydrous RuO2 particle films deposited on diamond and ZnSe prisms immersed in flowing aqueous solutions. The adsorption behaviour of oxalate has been shown to be very similar to that of oxalate adsorbing on TiO2 involving bidentate chelation. Adsorbed carbon monoxide exhibits several peaks indicating a diversity of sites as previously observed in its adsorption to RuO2 (110) under high vacuum. Adsorbed carbon dioxide/carbonate is formed from the oxidation of adsorbed CO. Both the adsorbed CO and adsorbed carbonate spectra are sensitive to the presence of CO and O2 as redox agents in solution which suggests that surface ruthenium ions may undergo changes in oxidation state via redox species in solution. These novel in situ spectroscopic results are the first from the RuO2 aqueous solution interface and will be discussed in comparison with those from surface science and electrochemistry.